[Quilt-dev] [PATCH v2] backup-files: Restore symbolic links

[Jean Delvare]

As "patch" originally did not handle symbolic links, backup-files
didn't have to care about them either. But now that git has
introduced an extended syntax which allows manipulating symbolic
links in patch files, "quilt push" may create or delete symbolic
links, which means that backup-files must support such operations
too.

Also extend the backup-files test case to cover these operations.

This fixes bug #59479:
https://savannah.nongnu.org/bugs/index.php?59479

Signed-off-by: Jean Delvare <jdelvare@suse.de>
---
The first version of the patch had portability issues as it used
non-POSIX options. It also did not fix the backup path of backup-files,
only the restore path was fixed. The new patch fixes both, in a
hopefully portable way.

 quilt/scripts/backup-files.in |   40 ++++++++++++++++++++++++++++++----------
 test/backup-files.test        |   33 +++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 10 deletions(-)

--- quilt.orig/quilt/scripts/backup-files.in    2020-11-24 19:58:20.750896064 
+0100
+++ quilt/quilt/scripts/backup-files.in 2020-11-26 12:47:18.647053943 +0100
@@ -89,7 +89,7 @@ backup()
        dir=$(dirname "$backup")
        [ -d "$dir" ] || mkdir -p "$dir"
 
-       if [ -e "$file" ]; then
+       if [ -L "$file" -o -e "$file" ]; then
                $ECHO "Copying $file"
                if [ -n "$OPT_NOLINKS" -a "$(stat @STAT_HARDLINK@ "$file")" = 1 
]; then
                        cp -p "$file" "$backup"
@@ -110,24 +110,28 @@ restore()
        local file=$1
        local backup=$OPT_PREFIX$file
 
-       if [ ! -e "$backup" ]; then
+       if [ ! -L "$backup" -a ! -e "$backup" ]; then
                return 1
        fi
-       if [ -s "$backup" ]; then
+       if [ -L "$backup" -o -s "$backup" ]; then
                $ECHO "Restoring $file"
-               if [ -e "$file" ]; then
+               if [ -L "$file" -o -e "$file" ]; then
                        rm "$file"
                else
                        mkdir -p "$(dirname "$file")"
                fi
-               ln "$backup" "$file" 2>&4 || cp -p "$backup" "$file"
+               if [ -L "$backup" ]; then
+                       ln -s "$(readlink "$backup")" "$file"
+               else
+                       ln "$backup" "$file" 2>&4 || cp -p "$backup" "$file"
+               fi
 
-               if [ -n "$OPT_TOUCH" ]; then
+               if [ -n "$OPT_TOUCH" -a ! -L "$file" ]; then
                        touch "$file"
                fi
        else
                $ECHO "Removing $file"
-               if [ -e "$file" ]; then
+               if [ -L "$file" -o -e "$file" ]; then
                        rm "$file"
                fi
        fi
@@ -145,11 +149,13 @@ restore_all()
        # Store the list of files to process
        EMPTY_FILES=$(gen_tempfile)
        NONEMPTY_FILES=$(gen_tempfile)
-       trap "rm -f \"$EMPTY_FILES\" \"$NONEMPTY_FILES\"" EXIT
+       LINK_FILES=$(gen_tempfile)
+       trap "rm -f \"$EMPTY_FILES\" \"$NONEMPTY_FILES\" \"$LINK_FILES\"" EXIT
 
        cd "$OPT_PREFIX"
        find . -type f -size 0 -print0 > "$EMPTY_FILES"
        find . -type f -size +0 -print0 > "$NONEMPTY_FILES"
+       find . -type l -print0 > "$LINK_FILES"
        cd "$OLDPWD"
 
        if [ -s "$EMPTY_FILES" ]; then
@@ -189,6 +195,20 @@ restore_all()
                fi
        fi
 
+       if [ -s "$LINK_FILES" ]; then
+               (cd "$OPT_PREFIX" && find . -type d -print0) \
+               | xargs -0 mkdir -p
+
+               while read -d $'\0' -r
+               do
+                       local file=${REPLY#./}
+                       local backup=$OPT_PREFIX$file
+
+                       $ECHO "Restoring $file"
+                       ln -sf "$(readlink "$backup")" "$file"
+               done < "$LINK_FILES"
+       fi
+
        if [ -z "$OPT_KEEP_BACKUP" ]; then
                rm -rf "$OPT_PREFIX"
        fi
@@ -212,7 +232,7 @@ copy()
        dir=$(dirname "$backup")
        [ -d "$dir" ] || mkdir -p "$dir"
 
-       if [ -e "$file" ]; then
+       if [ -L "$file" -o -e "$file" ]; then
                $ECHO "Copying $file"
                cp -p "$file" "$backup"
        else
@@ -234,7 +254,7 @@ copy_many()
        cat "$OPT_FILE" \
        | while read
        do
-               if [ -e "$REPLY" ]; then
+               if [ -L "$REPLY" -o -e "$REPLY" ]; then
                        printf '%s\0' "$REPLY" >&3
                else
                        # This is a rare case, not worth optimizing
--- quilt.orig/test/backup-files.test   2020-11-24 19:58:20.750896064 +0100
+++ quilt/test/backup-files.test        2020-11-26 12:35:26.945180538 +0100
@@ -229,3 +229,36 @@ Unit test of the backup-files script.
        > 1
        $ [ ! -s new ] || echo "file snapshot/new should be empty"
        $ rm -rf snapshot
+
+       # Test backup and restoration of a symbolic link
+       $ mkdir dir
+       $ ln -s foo dir/link
+       $ readlink dir/link
+       > foo
+       $ %{QUILT_DIR}/scripts/backup-files -B backup/ -b dir/link
+       > Copying dir/link
+       $ readlink backup/dir/link
+       > foo
+       $ rm -f dir/link
+       $ echo crap > dir/link
+       $ %{QUILT_DIR}/scripts/backup-files -B backup/ -r -k dir/link
+       > Restoring dir/link
+       $ readlink dir/link
+       > foo
+
+       # Same but reading from a file
+       $ rm -f dir/link
+       $ echo crap > dir/link
+       $ %{QUILT_DIR}/scripts/backup-files -B backup/ -r -k -f -
+       < dir/link
+       > Restoring dir/link
+       $ readlink dir/link
+       > foo
+
+       # Same but without specifying the file
+       $ rm -f dir/link
+       $ echo crap > dir/link
+       $ %{QUILT_DIR}/scripts/backup-files -B backup/ -r -
+       > Restoring dir/link
+       $ readlink dir/link
+       > foo


-- 
Jean Delvare
SUSE L3 Support